The
Laboratory
Bulbs
in
Series
Circuits
Lab
Teacher’s
Guide
Topic:
Electric
Circuits
The
following
information
is
provided
to
the
student:
Question:
When
a
low‐R
and
a
high‐R
bulb
are
placed
together
in
series,
which
is
brightest?
Why?
Which
is
brightest
when
they
are
alone
in
a
circuit?
Why?
How
do
the
voltage
drops
across
and
the
current
in
the
bulbs
compare?
How
do
these
measurements
support
the
observations
of
relative
brightness?
Purpose:
To
compare
the
brightness
of
low‐R
and
high‐R
bulbs
when
placed
together
in
series
and
to
compare
these
brightness
values
to
their
brightness
when
placed
alone
in
a
single‐bulb
circuit
AND
to
use
voltage
drop
and
current
measurements
to
explain
the
observed
differences.
A
complete
lab
write‐up
includes
a
Title,
a
Purpose,
a
Data
section,
and
a
Conclusion/Discussion
of
Results.
The
Data
section
should
include
labeled
schematic
diagrams
of
the
three
circuits
which
you
built
and
tested.
Voltmeter
arrangements
and
ammeter
placements
and
readings
should
be
recorded
on
your
diagram.
Observations
of
relative
brightness
should
be
recorded
on
the
diagrams
using
starburst
notations.
All
diagrams
should
be
organized,
legible
and
labeled.
The
Conclusion/Discussion
should
include
the
answer
to
the
questions
raised
in
the
purpose
accompanied
by
a
lengthy
explanation
of
why
one
bulb
was
brighter
than
another.
Explanations
should
reference
the
collected
data.
Materials
Required:
Two
D‐cells;
battery
holder;
alligator
leads;
two
small
~3
‐
5
V
bulbs
with
a
different
resistance;
bulb
bases;
computer
interfaced
ammeter
and
voltage
probes.
Description
of
Procedure:
A
series
circuit
is
constructed
using
two
bulbs
having
a
different
resistance.
An
ammeter
is
wired
into
the
circuit
in
series
with
the
two
bulbs.
Students
observe
and
record
the
brightness
of
the
low‐
resistance
and
the
high‐resistance
bulb.
Measurements
of
the
current
in
the
circuit
are
made.
The
voltage
probes
are
then
used
to
determine
the
voltage
drops
across
each
of
the
two
individual
bulbs
(∆Vlow
R
and
∆Vhigh
R).
Observations
and
measurements
of
current
and
voltage
drops
are
made
for
the
same
number
of
batteries
but
with
the
bulbs
placed
in
a
single‐bulb
circuit.
Students
use
the
measurements
to
help
explain
the
observations
and
to
answer
the
questions
posed
in
the
Purpose
of
this
lab.
Alternative
Materials
and
Procedure:
A
couple
of
multimeters
can
be
used
in
place
of
the
computer
interfaced
ammeter
and
voltmeter.
Safety
Concern:
©
The
Physics
Classroom,
2009
The
Laboratory
There
is
always
a
higher
than
usual
level
of
risk
associated
with
working
in
a
science
lab.
Teachers
should
be
aware
of
this
and
take
the
necessary
precautions
to
insure
that
the
working
environment
is
as
safe
as
possible.
Student
horseplay
and
off‐task
behaviors
should
not
be
tolerated.
Suggestions,
Precautions,
Notes:
1.
Use
the
same
bulbs
used
in
the
Round
vs.
Oblong
–
the
Greatest
Resistance?
Lab.
Students
should
have
a
record
in
their
lab
notebook
about
which
of
the
two
bulbs
have
the
greatest
resistance.
They
can
refer
to
this
record
in
order
to
complete
this
lab.
If
neither
computer
interfaced
probes
nor
multimeters
are
available,
then
there
is
great
merit
in
making
the
observations
and
altering
the
Purpose
in
such
a
manner
that
the
measurement
emphasis
is
removed.
2.
Auxiliary
Materials:
None
Scoring
Rubric:
C8.
Bulbs
in
Series
Circuits
Lab
Included,
labeled
and
organized
all
parts
of
the
lab
report.
Data
section
includes
schematic
diagrams
of
the
two‐bulb
series
circuit,
and
the
two
single‐bulb
circuits;
bulbs
are
labeled;
ammeter
locations
and
voltmeter
arrangements
are
indicated.
Relative
brightness
is
indicated
using
starburst
notation.
Measured
values
are
listed
on
the
diagram
and
labeled
as
∆Vlow
R,
∆Vhigh
R,
Ilow
R,
etc.
;
all
necessary
measurements
are
made;
units
are
given.
Diagrams
are
legible,
labeled
and
organized.
Conclusion/Discussion
answers
all
the
questions
posed
in
the
Purpose
(and
the
Questions
section).
All
comparisons
are
made.
Measured
data
is
used
to
explain
the
findings.
Discussion
is
complete
and
accurate;
reveals
understanding.
Connections
to
The
Physics
Classroom
Tutorial:
The
following
reading
is
a
suitable
accompaniment
to
this
lab:
http://www.physicsclassroom.com/Class/circuits/u9l4c.cfm
Connections
to
Minds
on
Physics
Internet
Modules:
Sublevels
7
and
9
of
the
Electric
Circuits
module
are
suitable
accompaniments
to
this
lab:
http://www.physicsclassroom.com/mop/module.cfm
©
The
Physics
Classroom,
2009
Score
_____/_____